A seat-belt retractor is described in DE 201 14 710 U1. If a seat-belt retractor of this type is, for example, installed in a vehicle seat where the backrest of the seat can be adjusted at an incline, then an inertial sensor for retractor locking may be provided with an alignment mass that can align itself when the angular position of the belt retractor is changed by adjusting the backrest to a vertical position, so that the response threshold of the sensor remains unchanged with regard to vehicle acceleration or deceleration. Since the sensor aligns and therefore adjusts itself during deceleration from braking, the seat-belt retractor is provided with a blocking device by means of which the sensor is automatically fixed whenever the belt is extended, because it is assumed that the belt will already have been extended early during an accident with a belt shaft rotating in the extension direction. In this type of seat-belt retractor, a two-legged friction spring, one leg of which is displaceably mounted on the seat-belt retractor and the other leg of which fits against a toothing configured on the sensor, is located on a friction disc connected to the belt shaft. The two-legged friction spring serves as a control and blocking device for the sensor mass. When the belt shaft rotates in the extension direction, the friction spring rotates into a position in which its leg fixes the sensor. Upon a reverse rotation of the belt shaft in the retraction direction, the friction spring likewise rotates in reverse with its blocking leg releasing the sensor again.
However, this seat-belt retractor has the disadvantage that fixing the sensor is effective only while the seat-belt extends, whereas the sensor is free for alignment displacement when the belt shaft is stopped.